---
title: "How do I compare two log files in PowerBI?"
url: "https://dm0bkdes5q7a2ls.productfruits.help/en/article/how-do-i-compare-two-log-files-in-powerbi"
language: "en"
last_updated: "2026-05-14T17:32:39.128Z"
---

# How do I compare two log files in PowerBI?

Comparing two log files in Power BI (for example, comparing a "Healthy" agent's logs to a "Failing" agent's logs, or comparing logs from before and after a configuration change) is one of the most powerful uses of the tool.

To do this effectively, you need to be able to view them side-by-side or overlaid on the same timeline.

## 1\. The Setup: Add a "Category" Column

When you ingest the 2 files, you must ensure Power BI knows which is which.

-   **If using the Folder Connector:** Power BI automatically provides the `Source.Name` column. Use this as your "Category."
-   **If importing files individually:** Manually add a custom column to each table (for example, `Status = "Healthy"` for one and `Status = "Failing"` for the other) before you append them together.

## 2\. The "Side-by-Side" Timeline (Area or Line Chart)

This is the best way to see **when** the two files started to behave differently.

-   **Axis:** Timestamp (Grouped by Minute or Hour).
-   **Values:** Count of Rows (or Count of Errors).
-   **Legend:** `Source.Name` (or your "Category" column).
-   **What to look for:** Look for the point where the "Failing" line spikes or flatlines while the "Healthy" line continues normally. This identifies the exact moment of divergence.

## 3\. The "Error Profile" Comparison (Clustered Bar Chart)

This helps you see if the *types* of errors are different between the two files.

-   **Y-Axis:** Message (The parsed log message).
-   **X-Axis:** Count of Rows.
-   **Legend:** `Source.Name`.
-   **What to look for:** If the "Failing" log has 500 "Socket Timeout" errors and the "Healthy" log has 0, you have found your smoking gun.

## 4\. The "Delta" View (Matrix Table)

A Matrix is the best way to see a direct count comparison of events.

-   **Rows:** Message (The log text).
-   **Columns:** `Source.Name`.
-   **Values:** Count of Message.
-   **Why it works:** This creates a spreadsheet-style view where you can see:
-   -   *Message A:* File 1 (10 times) | File 2 (12 times) — **Normal**
    -   *Message B:* File 1 (0 times) | File 2 (450 times) — **Critical Difference**

## 5\. Time-Shifting (Advanced)

If you are comparing two scans that happened at different times (for example, a scan on Monday vs. a scan on Tuesday), the timestamps won't line up on a chart.

-   **The Fix:** Create a "Relative Time" column in Power Query.
-   **How:** Calculate the time elapsed since the "Scan Started" marker for each file.
-   **Result:** You can now overlay the two scans on a chart starting at "Minute 0," allowing you to compare their performance second-for-second regardless of when they actually ran.

* * *

## **SME Comparison Checklist**

| Comparison Goal | Best Visual | Key Metric |
| --- | --- | --- |
| **When did it break?** | **Line Chart** | Count of Errors over Time |
| **What is the difference?** | **Clustered Bar Chart** | Top Error Messages by File |
| **Is one slower?** | **Gantt or Bar Chart** | Time between "Start" and "End" markers |
| **Direct count check** | **Matrix Table** | Count of specific events per file |

**Summary:** To compare two logs, **Append** them into a single table, keep a **Source Name** column to distinguish them, and use **Clustered Bar Charts** or **Matrix Tables** to highlight the differences in error types and frequency.